from fastapi import FastAPI
from pydantic import BaseModel

class Item(BaseModel):#json格式
    name: str
    description: str | None= None
    price: float
    tax: float | None= None

app = FastAPI()

@app.post("/items/")
async def create_item(item: Item):
    item_dict = item.dict()
    if item.tax is not None:
        price_with_tax = item.price + item.tax
        item_dict.update({"price_with_tax": price_with_tax})
    return item_dict